1. Field of Invention
The present invention relates to liquid crystal devices for performing gray-scale display by simultaneously selecting a plurality of scanning electrodes, electro-optical devices, driving circuits and driving methods therefor, and electronic apparatuses.
2. Description of Related Art
Currently, liquid crystal devices can be classified into various types depending on the electrode configuration and driving methods. For example, matrix liquid crystal devices can generally be classified into two types: 1) active matrix devices using switching elements, such as transistors, and diodes, and 2) passive matrix devices not using switching elements. Of the two types, passive matrix devices do not use switching elements, and are thus advantageous in that they are suitable for reducing power consumption and can be manufactured easily at low cost.
A known driving method for such passive matrix liquid crystal devices involves simultaneously selecting a plurality of scanning electrodes in order to increase contrast and to achieve low-voltage driving (hereinafter referred to as an “MLS driving method”).
In the driving method involving simultaneously selecting a plurality of scanning electrodes, as the number of scanning electrodes to be simultaneously selected increases, so does the number of voltage levels available for a data signal to be supplied to a signal electrode. For example, when a method for simultaneously selecting four scanning electrodes is used, a data signal can be at five voltage levels. When the number of voltage levels of each data signal increases, the configuration of a signal electrode driving circuit becomes more complicated, or the manufacturing cost or the power consumption increase.
By way of example, Japanese Unexamined Patent Publication H10-133630 discloses a technology for solving the above-described problems caused by an increase in the number of voltages and performing gray-scale display using the MLS driving method. According to the technology disclosed, the calculation shown in FIG. 19 is performed wherein L denotes the number of simultaneously-selected electrodes, N denotes the number of gray levels, D denotes gray-scale data, and F denotes an orthogonal coefficient, thus obtaining data indicating, for how long, which of two voltage types should be applied to a signal electrode. Accordingly, gray-scale display can be performed while reducing the number of voltage levels of each data signal. Adoption of this technology requires an arithmetic circuit for performing the complicated calculation processing shown in FIG. 19. As a result, additional problems such as an increase in the manufacturing cost and an increase in the circuit size accompanied with more complicated circuit configuration occur.